Biguanides (Metformin)

Endocrine & Metabolic

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Examples

metformin

Prefix / Suffix: No consistent suffix

Physiology

Insulin resistance in type 2 diabetes leads to elevated hepatic glucose production and impaired peripheral glucose uptake.

Mechanism of Action

Decreases hepatic glucose production, decreases intestinal glucose absorption, and improves insulin sensitivity. Does not stimulate insulin release.

Indications

First-line for type 2 diabetes
Polycystic ovary syndrome (PCOS)
Prediabetes

Side Effects / Adverse Effects

GI upset (nausea, diarrhea, metallic taste — common, usually transient)
Vitamin B12 deficiency (long-term)
Lactic acidosis (rare but serious — especially with renal impairment)
Does NOT cause hypoglycemia as monotherapy

Contraindications

Severe renal impairment (eGFR <30)
Acute or chronic metabolic acidosis
Severe hepatic impairment
Hold before contrast dye procedures (lactic acidosis risk)

Nursing Considerations

Take with meals to reduce GI side effects
Hold 48 hours before and after IV contrast — restart after kidney function confirmed
Monitor renal function (creatinine, eGFR) at baseline and yearly
Monitor B12 levels with long-term use
Teach signs of lactic acidosis: muscle pain, weakness, trouble breathing, unusual sleepiness
Avoid excessive alcohol (increases lactic acidosis risk)

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